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Case 646 Lacking Hydraulic power help needed

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#21 ·
Remove one of the quick couplers from the TILLER.

Use fittings to adapt the gauge to that quick coupler.

Plug the quick coupler into the mating half coupler on the rear PTO VALVE.


Start the engine and run it at 1/4 throttle.

Move the PTO lever off the centre (neutral) position while watching the gauge.

If the gauge needle moves, then you have found the correct side of the PTO for the test. Move the handle back to neutral.

If the gauge needle does not move, then flip the handle to the opposite side of neutral and then when you see the needle move, put the lever back into neutral.

Then, run the engine at full speed.

Move the PTO handle back to the side that showed needle movement. Record the pressure noted on the gauge and return the lever to neutral.

Allow the tractor to run for 10 to 15 minutes until the hydraulic oil reaches operating temperature of at least 125 degrees F. You can use an oven thermometer to check this.. These are the ones with a sharp probe designed to be pushed into roasts. The Dollar Store has them.

Repeat the above test.

Cold oil should read higher than hot oil when the PSI is measured.

Post the readings back here in this thread.
 
#22 ·
In addition to Hydriv's test above I'd add the following...

Assuming this machine is equipped with mid-lift...

-Verify you have a TCV with Power Beyond and it is routed correctly

-Place axle in open/neutral with travel lever in center/neutral
-Move mid-lift lever fully to one direction until cylinder bottoms
-is relief opening?
-what is pressure measurement on gage?
-Same as above except mid-lift lever in opposite direction

-Place mid-lift in center position
-Move loader lift circuit in one direction until bottoms
-is relief opening?
-what is pressure at?
-Same as above but opposite direction
-Do the same for bucket circuit
 
Discussion starter · #23 ·
Thanks for the directions, any testing will have to wait as the pto hose cracked, it must have been really bad as I hardly moved it.
I did not get the guage hooked up where I wanted to put it,
I got it on the hoses that used to go to the tiller and all I got was about 300psi or so.
 
#24 ·
If your tiller was NOT connected to the tractor in any way and you put the gauge at the end of a hose that is connected to the PTO valve, then it sounds as though you have it installed correctly. If the hose does not leak when you move the PTO lever to supply oil to that hose, then I wouldn't worry about the hose for the moment.

Did you run the engine at full throttle? If so and all you got was 300 PSI, then the pump must be shot. You should be seeing about 2600 PSI on that gauge if everything is working properly. Here is a replacement pump.

http://www.grainger.com/Grainger/wwg/se ... earch.y=10
 
Discussion starter · #25 ·
ok, i had the gauge "T"d into the circuit if you know what I mean?
when I tilted the bucket all the way up or down until it stopped the gauge hit around 1200, i was going to "T" it into the PTO circuit but the braided hose cracked.
I really don't see any other area to hook the guage into without have some really special fittings
sorry if I sound dumb but this hydraulic stuff is all new to me. thanks for your input and advice. MIke
 
#26 ·
Yes.... I understand what you mean when you say you had it T'd into a circuit. When testing the pressure in the loader circuits, it's perfectly OK to install a Tee fitting on one of the lines going to a cylinder/s and then run that cylinder/s to the very end of its travel and keep applying the oil pressure. The loader has a relief valve that is supposed to pop at 1200 PSI so it sounds as though your pump can generate at least that much pressure. However, the pump FEEDS the rear PTO valve FIRST and that's the spot you want to test FIRST because that's where you will find out whether the pump is good or bad.

If you have two hoses leaving that PTO that go to quick couplers that are screwed onto the tiller, then remove one of those quick couplers from the tiller motor and then go to your local hydraulics store and get a fitting that will transition that coupler to the gauge. Then plug that gauge into the hose once you have replaced that hose.
 
#27 ·
So the relief for the loader is OK and set approx 1200 psi.

Should be able to check the others by 'T'ing in at the test/drain plug in TCV. That way you'll know they're set right. The lift circuit relief should be higher than the loader circuit relief.
 
#28 ·
I have been digging a trench all day all was working as it should .Oh I have a 75 case 646 loader backhoe .I shut it down to eat dinner then went back out after dinner and the boom on the backhoe will not stay up ,when I release the handle it drops like a rock and it has no power to lift it will extend and the bucket works fully extended bucket full will not lift fully extended bucket empty it will lift as lone as you pull back on the lever but when you let it go it drops please help I only have to dig 14' more and I'm done
 
#29 ·
Mrcedy,
Welcome aboard. Not quite sure why you're buried in this old post, but whatever...

Since you seem to have an issue just isolated to the the boom, there are only a few things that could be the cause as far as I can imagine.
  • You might have lost a seal in the boom cylinder.
  • You might have lost one of the relief valves in the Boom section of the stack valve.
  • You might have an issue with the Boom section itself. (I really doubt that)

Regardless, you aren't going to be finishing that ditch today, or tomorrow... Support for the valve stack is just about zero. If it is the relief you might get lucky checking with member LJohnSaw as I semi-recently sent him my entire stack valve assembly when I had to replace it due to a cracked outlet section. I don't know which sections he used for his project.

Good luck!
 
#30 ·
Are new Banana plates being made?
My 646 doesn't move very good lacking power in forward or reverse.
I have not had it apart yet but will take it apart in the Spring( a little cold now in MN).
I bought a drive motor for it last week and i'm looking for any other parts in the drive linkage.
Thanks
 
#31 ·
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bhildret
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